This invention relates to general to photoelectrophoretic imaging machines and, more particularly, an improved web device color copier photoelectrophoretic imaging machine.
In the photoelectrophoretic imaging process, monochromatic including black and white or full color images are formed through the use of photoelectrophoresis. An extensive and detailed description of the photoelectrophoretic process is found in U.S. Pat. Nos. 3,384,488 and 3,383,565 to Tulagin and Carreira; 3,383,993 to Yeh and 3,384,566 to Clark, which disclose a system where photoelectrophoretic particles migrate in image configuration providing a visible image at one or both of two electrodes between which the particles suspended within an insulating carrier is placed. The particles are electrically photosensitive and are believed to bear a net electrical charge while suspended which causes them to be attracted to one electrode and apparently undergo a net change in polarity upon exposure to activating electromagnetic radiation. The particles will migrate from one of the electrodes under the influence of an electric field through the liquid carrier to the other electrode.
The photoelectrophoretic imaging process is either monochromatic or polychromatic depending upon whether the photosensitive particles within the liquid carrier are responsive to the same or different portions of the light spectrum. A full-color polychromatic system is obtained, for example, by using cyan, magenta and yellow colored particles which are responsive to red, green and blue light respectively.
In photoelectrophoretic imaging generally, and as employed in the instant invention, the important broad teachings in the following five paragraphs should be noted.
Preferably, as taught in the four patents referred to above, the electric field across the imaging suspension is applied between electrodes having certain preferred properties, i.e., an injecting electrode and blocking electrode, and the exposure to activating radiation occurs simultaneously with field application. However, as taught in various of the four patents referred to above and Luebbe et al, U.S. Pat. No. 3,595,770; Keller et al, U.S. Pat. No. 3,647,659 and Carreira et al, U.S. Pat. No. 3,477,934, such a wide variety of materials and modes for associating an electrical bias therewith, e.g., charged insulating webs, may serve as the electrodes, i.e., the means for applying the electric field across the imaging suspension, that opposed electrodes generally can be used; and that exposure and electrical field applying steps may be sequential. In preferred embodiments herein, one electrode may be referred to as the injecting electrode and the opposite electrode as the blocking electrode. This is a preferred embodiment description. The terms blocking electrode and injecting electrode should be understood and interpreted in the context of the above comments throughout the specification and claims hereof.
It should also be noted that any suitable electrically photosensitive particles may be used. Kaprelian, U.S. Pat. No. 2,940,847 and Yeh, U.S. Pat. No. 3,681,064 disclose various electrically photosensitive particles, as do the four patents first referred to above.
In a preferred mode, at least one of the electrodes is transparent, which also encompasses partial transparency that is sufficient to pass enough electromagnetic radiation to cause photoelectrophoretic imaging. However, as described in Weigl, U.S. Pat. No. 3,616,390, both electrodes may be opaque.
Preferably, the injecting electrode is grounded and a suitable source of difference of potential between injecting and blocking electrodes is used to provide the field for imaging. However, such a wide variety of variations in how the field may be applied can be used, including grounding the blocking electrode and biasing the injecting electrode, biasing both electrodes with different bias values of the same polarity, biasing one electrode at one polarity and biasing the other at the opposite polarity of the same or different values, that just applying sufficient field for imaging can be used.
The photoelectrophoretic imaging system disclosed in the above-identified patents may utilize a wide variety of electrode configurations including a transparent flat electrode configuration for one of the electrodes, a flat plate or roller for the other electrode used in establishing the electric field across the imaging suspension.
The photoelectrophoretic imaging system of this invention utilizes web materials, which optimally may be disposable. In this system, the desired, e.g., positive image, is formed on one of the webs and another web will carry away the negative or unwanted image. The positive image can be fixed to the web upon which it is formed or the image transferred to a suitable backing such as paper. The web which carries the negative image can be rewound and later disposed of. In this successive color copier photoelectrophoretic imaging system employing consumable webs, cleaning systems are not required.
Web machine patents may be found in the photoelectrophoretic, electrophotography, electrophoresis and coating arts. In the photoelectrophoresis area is Mihajlov U.S. Pat. No. 3,427,242. This patent discloses continuous photoelectrophoretic apparatus but using rotary drums for the injecting and blocking electrodes instead of webs. The patent to Mihajlov also suggests the elimination of cleaning apparatus by passing a web substrate between the two solid rotary injecting and blocking electrodes. U.S. Pat. No. 3,586,615 to Carreira suggests that the blocking electrode may be in the form of a continuous belt. U.S. Pat. No. 3,719,484 to Egnaczak discloses continuous photoelectrophoretic imaging process utilizing a closed loop conductive web as the blocking electrode in conjunction with a rotary drum injecting electrode. This system uses a continuous web cleaning system but suggests consumable webs in place of disclosed continuous webs to eliminate the necessity for cleaning apparatus. U.S. Pat. No. 3,697,409 to Weigl discloses photoelectrophoretic imaging using a closed loop or continuous injecting web in direct contact with a roller electrode and suggests that the injecting web may also be wound between two spools. U.S. Pat. No. 3,697,408 discloses photoelectrophoretic imaging using a single web but only one solid piece. Pat. No. 3,702,289 discloses the use of two webs but two solid surfaces. U.S. Pat. No. 3,477,934 to Carreira discloses that a sheet of insulating material may be arranged on the injecting electrode during photoelectrophoretic imaging. The insulating material may comprise, inter alia, baryta paper, cellulose acetate or polyethylene coated papers. Exposure may be made through the injecting electrode or blocking electrode. U.S. Pat. NO. 3,664,941 to Jelfo teaches that bond paper may be attached to the blocking electrode during imaging and that exposure could be through the blocking electrode where it is optically transparent. This patent further teaches that the image may be formed on a removable paper substrate or sleeve superimposed or wrapped around a blocking electrode or otherwise in the position between the electrode at the site of imaging.
U.S. Pat. No. 3,772,013 to Wells discloses a photoelectrophoretic stimulated imaging process and teaches that a paper sheet may comprise the insulating film for one of the electrodes and also discloses that exposure may be made through this electrode. This insulating film may be removed from the apparatus and the image fused thereto.
U.S. Pat. Nos. 3,761,174 and 3,642,363 to Davidson disclose apparatus for effecting the manifold imaging process wherein an image is formed by the selective transfer of a layer of imaging material sandwiched between donor and receiver webs.
U.S. Pat. Nos. 2,376,922 to King; 3,166,420 to Clark; U.S. Pat. Nos. 3,182,591 to Carlson and 3,598,597 to Robinson are patents representative of web machines found mostly in the general realm of electrophotography. These patents disclose the broad concept of bringing two webs together, applying a light image thereto at the point of contact and by the application of an electric field effecting a selective imagewise transfer of toner from one web to the other.